Optimization of design parameters of a prototype CCD-based lens-coupled imaging system for the detection of beta particles in a microfluidic chip

Microfluidic chips are an emerging technology that facilitates the study of molecular processes in nano-liter levels in a finely controlled manner. A prototype imaging system capable of detecting and quantifying very small amounts of beta particles in a microfluidic chip, utilizing a scintillator, an optical lens, and a charge coupled device (CCD), was developed and proof of concept was previously demonstrated [1]. In this study, we optimized the system design parameters, such as CCD binning and types of scintillators, and evaluated the system performance for spatial resolution and minimum detectable activity. Pixel binning of the CCD during readout process improved the signal-to-noise ratio with no spatial resolution degradation in beta particle imaging of 18F, up to a binning of 3times3 in our study, which was equivalent to 44 mum times 44 mum pixels in an object plane with a magnification of 0.5. The full width at half maximum (FWHM) of line sources with a finite width of 115 mum were measured to be 493 mum with a plastic scintillator and 289 mum with a CsI(Tl) scintillator. The minimum detectable activities were measured to be 360 pCi/mm2 with a plastic scintillator and 40 pCi/mm2 with a CsI(Tl) scintillator for a 5-min acquisition.